1. Technical Field
The present disclosure relates to dimming lighting circuits and luminaires, and relates in particular to a dimming lighting circuit and a luminaire which receive a phase-controlled AC voltage and supplies a light source with a DC current.
2. Description of the Related Art
For phase-control dimming lighting circuits, which receive a phase-controlled AC voltage and supply a light source with a DC current, techniques for solving various problems caused by phase control have been proposed (see Patent Literature 1 (PTL 1): Japanese Unexamined Patent Application Publication No. 2008-104273, for example).
The dimming lighting circuit disclosed in PTL 1 includes: a phase detection circuit which detects a conduction phase angle in phase control in one half cycle of the supplied AC voltage; and a control unit which controls a DC output current of a DC-DC converter circuit by constant current control based on the detection output of the phase detection circuit. This makes it possible to control the DC output current to cause the DC output current not to fluctuate at every half cycle of the AC voltage even when the conduction phase angle in the phase control in one half cycle of the phase-controlled AC voltage and the conduction phase angle in the phase control in the other half cycle of the phase-controlled AC voltage are not exactly the same. This yields an advantageous effect that fluctuations of light output are less noticeable even when the dimming level is low.